Anyone dumping waste at landfill sites throughout the State, including local authorities, must now pay a levy of €15 per tonne.
The proceeds will go to a "ring-fenced" fund to finance a range of environmental initiatives.
A spokesman for the Department of the Environment said the new levy was designed to implement the "polluter pays" principle.
It would also promote alternatives to dumping, notably recycling. It came into effect on June 1st,
The landfill levy has been welcomed by Mr Andrew Hetherington, chief executive of Repak, the industry-funded packaging waste compliance scheme.
He said it would help meet recycling targets as laid down by the EU.
"Repak, on behalf of its members, met Ireland's targets last year," he said.
"However, these targets are due to double by 2005, and with the lack of recycling infrastructure the country is facing a significant challenge in meeting its future targets".
Mr Hetherington said the introduction of the landfill levy offered "a tangible incentive to industry and the public to segregate and offer their packaging waste for recycling, rather than facing ever increasing landfill charges".
With these charges already running at up to €100 per tonne, there has been concern that unscrupulous waste contractors would seek alternatives to designated landfill. Sites such as a number of disused quarries in Co Wicklow have already been used for this purpose.
To deter non-compliance with the 1998 Waste Management Act, the Minister for the Environment, Mr Dempsey, made regulations last autumn requiring all contractors to obtain permits for the transportation of waste.
The National Criminal Investigation Bureau is also conducting a wide-ranging inquiry into illegal dumping in Co Wicklow and elsewhere.
Anyone found guilty could face a fine of up to €12.7 million and/or 10 years in prison.
The new landfill levy, together with the 15 cent tax on plastic bags which was introduced earlier this year, is expected to raise €30 million per year for an environment fund to finance the development of recycling and other initiatives.
